NATO Deputy Secretary-General Alexander Vershbow has warned against attempts to bolster Moscow-backed rebels in Moldova as Kyiv scrambles to quell a separatist uprising in eastern Ukraine.

Speaking to RFE/RL ahead of his visit to Moldova next week, Vershbow said Moldova was facing "increasing pressure" due to the crisis in Ukraine.

He called on Moscow to "respect Moldova's territorial integrity" and said the alliance would look "very negatively" at any attempt to bring Moldova's breakaway Transdniester region "closer to Russia."

Vershbow said he would discuss efforts to increase Moldova's military capacities during his visit to Chisinau.

Moldova is not a NATO member but joined the alliance's Partnership for Peace program in 1994.

The standoff in Ukraine, where government troops have been fighting rebels in the Russian-leaning east following Russia's annexation of Crimea, has sparked fears Transdniester could be Moscow's next target.

NATO's supreme allied commander in Europe, U.S. Air Force General Philip Breedlove, warned in March that Russian troops massed on Ukraine's eastern border were well positioned to invade Transdniester.